A conventional power conversion apparatus for converting an AC voltage to a DC voltage includes a full-wave rectification circuit and a converter. A full-wave rectification circuit is connected to an AC power supply, and performs full-wave rectification of alternating current from an AC power supply. A converter converts the voltage full-wave rectified by a full-wave rectification circuit to a desired DC voltage. A converter supplies the DC voltage to a load.
As described above, a conventional power conversion apparatus obtains a desired DC voltage by applying a full-wave rectified alternating current to a converter. A diode bridge circuit is used for full-wave rectification. In a diode bridge circuit, a current always flows through a series circuit comprising two diodes regardless of whether an AC voltage is positive or negative. At this time, a power loss equivalent to the product of a current flowing through each diode and a forward voltage in a diode occurs in two diodes.
To prevent such a power loss, it is considerable to apply an alternating current to a converter without full-wave rectification. However, in such a case, an input voltage and input current to a converter are reverse in polarity, positive and negative.
A conventional power conversion apparatus applies a pulsating current or direct current after full-wave rectification. Thus, a converter may accept only a positive input voltage and current. In other words, a converter used in a conventional power conversion apparatus may not accept a negative input voltage and current. A power conversion apparatus able to apply an alternating current to a converter without full-wave rectification has not been realized.